This invention is directed to a method of purification and decolorization of sugar liquors.
This invention especially relates to an improved method for the purification and decolorization of sugar liquors including starch hydrolyzates such as corn syrup.
More particularly, this invention provides for a purification of sugar liquors through the use of a special granular activated carbon resulting in final products of high purity.
The term, "sugar liquors," as used herein, includes solutions of starch hydrolyzate which contain a mixture of mono-, di-, and higher polysaccharides and it particularly includes sugar solutions derived from cane, beet and corn sources. The term, "oligosaccharide," as used herein, is a carbohydrate containing from 2 to 8 simple sugars linked together. Combinations of more that 8 simple sugars are polysaccharides. A starch hydrolyzate is defined as an aqueous mixture of sugar components derived from acid, enzyme or other treatment of starchy materials.
The purification of sugar liquors such as corn syrup, cane sugar and relatively impure solutions of dextrose is one of the oldest established industrial chemical procedures.
Aqueous solutions of certain sugars such as glucose occur industrially in the hydrolysis of amylaceous or cellulosic materials. For example, large quantities of glucose solutions are prepared by the hydrolysis of starch in the manufacture of corn syrup, corn sugar and dextrose. These solutions contain minor but significant amounts of other sugars not removed by conventional refining procedures.
One use for activated carbon is the decolorization of sugar liquors. Typically the powdered activated carbon is slurried with the impure liquor one or more times followed by filtration of the decolorized liquor. Decolorization is also accomplished by passing the liquors through a column of granular activated carbon. These procedures remove color-causing impurities but only incidental amounts of oligosaccharides present in the liquor.
Another use of activated carbon involves the adsorption of high molecular weight sugars in addition to color causing impurities. Activated carbon has been employed in a column chromatography system for removing such impurities from a glucose solution as described in U.S. Pat. No. 2,549,840. Cakes of powdered activated carbon have been used in a series of filters to accomplish the removal of impurities from sugar liquors as described in U.S. Pat. No. 3,551,203.
These purification techniques generally require either a large amount of activated carbon or suffer from low flow rates, resulting in a poor yield or purified sugar product.